Rj12 Wiring Diagram Using Cat5. For a uk telephone to be connected to an rj45 socket a converter adaptor must be used. The correct wiring of a rj45 to rj11 (certainly in the uk)is to use the middle two pins (3/4) on the rj11 and use the blue. Rj45 Tool Kit Network Cable Tester Rj45 […]